1. Field of the Invention
The present invention is generally related to inspection systems for objects, and more particularly to such inspection systems that automatically inspect moving products or the like by using video cameras or the like.
2. Description of the Prior Art
During the recent years, the inspection of components or products or the like has advanced with a trend to provide labour savings at the inspection processes, or further to the "no man" operations, by changes from the human dependent visual inspection to automatic inspection by image signal processing of the utilized photo sensors or video cameras or the like. At present, where various production processes for such products are increasingly commenced with high speeds, the inspection processes are required to cope with these increased high speeds.
Attempts have been proposed to inspect such products that flow with high speed on conveyers or the like, by using video cameras as an example. At such systems, stroboscopes or the like are used as the lighting source to irradiate on the products for a short time period, so that the product may be caught as a static image on the photo sensing or target screen of the video camera, and then by processing the image signal delivered from the video camera, conducts the product inspection.
In the case of inspecting products or the like by video cameras, it is normally necessary to throw light onto the products. As for such lighting methods, there are various methods of irradiation, such as reflection lighting or through lighting and others, but in order to accurately inspect such products by video cameras or the like, it is an important condition that the intensity of the light irradiating on the products are constant.
Even when the light intensity for lighting from the light source is constant, an accurate inspection cannot be expected if the light intensity that enters the video camera is not constant after reflection from the product to be inspected or through passing the product. As an example, in the case of reflection lighting use, although the light intensity from the light source is constant, the reflection light intensity varies depending upon the base colour of the object under irradiation. On the other hand, in the case of a through lighting method, although the intensity from the light source is constant, for instance, such as in the case of glass bottle inspection (bottle bottom, bottle body), the intensity of the light passing there through will vary by the colour irregularities of the coloured bottles.
At the conventional systems, there is no compensation or counter measures to deal with variations in the light intensities that are picked up by the video camera. Accordingly in such above cases, an accurate inspection cannot be anticipated.